Mechanism of the oxidation of heptafulvenes to tropones studied by online mass spectrometry and density functional theory calculations
Nilsson, Sofia M. E.; Henschel, Henning; Scotti, Gianmario; Haapala, Markus; Kiriazis, Alexandros; Boije af Gennäs, Gustav; Kotiaho, Tapio; Yli-Kauhaluoma, Jari (2019-09-27)
Mechanism of the Oxidation of Heptafulvenes to Tropones Studied by Online Mass Spectrometry and Density Functional Theory Calculations Sofia M. E. Nilsson, Henning Henschel, Gianmario Scotti, Markus Haapala, Alexandros Kiriazis, Gustav Boije af Gennäs, Tapio Kotiaho, and Jari Yli-Kauhaluoma The Journal of Organic Chemistry 2019 84 (21), 13975-13982 DOI: 10.1021/acs.joc.9b02078
© 2019 American Chemical Society. This is an open access article published under Creative Commons (CC-BY) Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the author and source are cited.
https://creativecommons.org/licenses/by/4.0/
https://urn.fi/URN:NBN:fi-fe2021111755787
Tiivistelmä
Abstract
We have identified the most likely reaction mechanism for oxidizing heptafulvenes to the corresponding tropones by experimental and theoretical investigations. The experimental studies were done by coupling a three-dimensional printed miniaturized reactor with an integrated electrospray ionization needle to a mass spectrometer. Using the experimentally observed ions as a basis, nine alternative reaction pathways were investigated with density functional theory calculations. The lowest energy reaction pathway starts with the formation of an epoxide that is opened upon the addition of a second equivalent of the oxidizing species meta-chloroperoxybenzoic acid. The adduct formed then undergoes a Criegee-like rearrangement to yield a positively charged hemiketal, which on deprotonation dissociates into acetone and tropone. Overall, the reaction mechanism resembles a Hock-like rearrangement.
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